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Intermittent squealing

JG1966

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So, I started up the 340 today and got a horrible squealing sound from the front of the motor. Sounded like bad/loose belts on steroids or the water pump was about to explode. It went away in about 10-15 seconds before I could pinpoint it. I drove around and got the same squealing -- but not nearly as bad -- when I would lightly accelerate. I pulled over, popped hood to narrow it down and, of course, the sound went away before I could get there. But just about everytime I lightly accelerate I got the squeal.
When I gave it more gas, the squeal either went away or I couldn't hear it over the motor.
My water pump is old and it's probably time for a new one, but I'm trying to narrow it down. The last four times I started it, no squeal at all. When I raise RPMs in park, no squeal.
The belts are tight and relatively new but I guess it's possible they are the culprit. Oil pressure is good, oil is clean and no fluids are leaking underneath (or out the water pump). Power steering fluid is filled. Any suggestions based on the fact it mainly happens at light acceleration? The fact it only happens when the motor is under a load has me a bit confused -- and maybe concerned. Only once did it happen right at start up and I can't get it to squeal at idle, whether in park or drive, to locate it. Thanks

Update: My battery isn't charging, so I think I know my problem
 
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did you try taking off the belts and see if it still made the noise. One belt at a time. Dont drive it just see if the noise stops and go from there.
 
did you try taking off the belts and see if it still made the noise. One belt at a time. Dont drive it just see if the noise stops and go from there.
Thanks Davek. I just checked my voltage at the battery in case it was the alternator making the sound and I'm only charging at 12.5 V. I'm getting same voltage at the power stud on the alternator. I'm pretty sure my alternator bearings are toast
 
unhook the belt and see
 
Got to love these cars :lol:
Right!?!? They keep us on our toes, that's for sure. I just tested the alternator by grounding the alternator blue field terminal, started the engine and checked voltage at battery. Still 12.5. I'm pretty sure that means bad alternator.
 
If you had of left the green field ground on and removed the blue field wire the alternator would have gone full field and been putting out 18 volts or so. You don't ground the second field spade it gets 12v+ on the blue wire. Sounds like your green field/ground wire is off somewhere or the regulator is pouched. I had my blue wire break off at the regulator connector last year and she went full charge on me..
 
What a coincidence. I've had the banshee squeal for some time and just a couple weeks ago decided to remove the belts to see what happened. Squeal went away so put both belts back on and still no squeal. Only thing I can think of was the alternator belt was too tight. Guess there is a too loose - too tight window!! Either way, I'm happy now.
 
If you had of left the green field ground on and removed the blue field wire the alternator would have gone full field and been putting out 18 volts or so. You don't ground the second field spade it gets 12v+ on the blue wire. Sounds like your green field/ground wire is off somewhere or the regulator is pouched. I had my blue wire break off at the regulator connector last year and she went full charge on me..
Thanks Dadsbee. I think it's my wires. When I probe the back of the green wire with key on run, I get about 10.5V. When I probe the back of blue wire, I get nothing, 0V.
 
What a coincidence. I've had the banshee squeal for some time and just a couple weeks ago decided to remove the belts to see what happened. Squeal went away so put both belts back on and still no squeal. Only thing I can think of was the alternator belt was too tight. Guess there is a too loose - too tight window!! Either way, I'm happy now.
Thanks Gold Rush. I got the alternator charging again. Not sure what fixed it, but it's all good (I think something was just loose somewhere). I'm now getting the squeal in park when I give it gas. Sounds like it's coming from bottom of water pump/balancer/crank pulley. Now that I can get it to squeal, I'm gonna pull belts and see what happens.
 
Check the condition of the belts and the pulleys. Take the belts off and inspect them for a glazed appearance (signs of slipping), bend them backwards and look for cracking or separations. Belts like other parts made today do not have the quality of the past.

Check to alignment of pulleys with a straight edge or a tape measure and make sure they’re not riding low in the pulleys (sign of worn pulley).

never mind. I just read your last post!!
 
What a coincidence. I've had the banshee squeal for some time and just a couple weeks ago decided to remove the belts to see what happened. Squeal went away so put both belts back on and still no squeal. Only thing I can think of was the alternator belt was too tight. Guess there is a too loose - too tight window!! Either way, I'm happy now.
I took belts off and I'm still getting the squeal. At least that narrows it down
 
Check the condition of the belts and the pulleys. Take the belts off and inspect them for a glazed appearance (signs of slipping), bend them backwards and look for cracking or separations. Belts like other parts made today do not have the quality of the past.

Check to alignment of pulleys with a straight edge or a tape measure and make sure they’re not riding low in the pulleys (sign of worn pulley).

never mind. I just read your last post!!
Thanks Moms 68. I have a question. I took belts off and am still getting the squeal when I give a little gas from idle. Wouldn't that mean it can't be the water pump? Does water pump still "spin" with no belts hooked up?
 
51F285DE-712F-45C2-BE11-592B12C23690.jpeg
Attached is a photo of my 340 with power steering. With no belts only the crankshaft would be moving.
 
belt off then pump is not moving. Did you change anything in the last couple months?
 
belt off then pump is not moving. Did you change anything in the last couple months?
No. The only think that happened of note is I blew a little hole in the 1/2 inch rubber cap that blocks my unused heater hose outlet on my water pump. I got a little bit of coolant on the fan and radiator but nothing huge. I caught it very quickly. That's about it. The good thing is the squeal is annoying but it doesn't sound like something catastrophic involving the motor. When I had the belts off, I tried to wiggle the fan and the crank pulley and the harmonic balancer. Everything was very tight.
 
ok lets try this are you sure its up front? good oil pressure ? auto or 4 spd?
 
ok lets try this are you sure its up front? good oil pressure ? auto or 4 spd?
Oil pressure was first thing I checked, because that's where my concerns were. It's fine. Hasn't changed. Varies between about 40-60 psi ( that's where it always is). It's a 727. I wouldn't bet my life it's coming from the front but I'd probably bet my left nut. I'm 98.9% sure it's not coming from the tranny
 
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